I am obsessed with not getting cancer. I don’t smoke; I avoid deli meats. I even stopped eating bananas to off-set working with radiation in the lab. Turns out, I might be completely wasting my time.

A new study in Science from a group at Johns Hopkins revealed that the most likely cause of cancer lies with the normal, random mistakes made during DNA replication. By analyzing 17 different cancers in 69 different countries, scientists explored the relative contribution of hereditary, environmental factors, and lifetime number of stem cell divisions to the incidence of cancer. The study encompassed 4.8 billion people. Stem cell divisions were strongly associated with cancer development, producing a median correlation of 0.80. Since this correlation increased with age and the division rate of many cell types does not (i.e. bone and brain), the scientists reason it must be the lifetime number of cell divisions that contributes to the cancer odds.

The analysis was rooted in the fact that cancers typically acquire multiple mutations other than the “driver” mutation, or most important, for oncogenesis. While the environment contributes considerably (especially to specific cancers such as lung adenocarcinomas), the driver mutation may actually target the rate of somatic replication, thereby directly resulting in increased risk of replication mistakes.

I found this study to be equally comforting and terrifying. However, it was interesting that the lowest age presented was a bracket between 0-70. I wonder if the same analysis was conducted in brackets of 10 or 20 years, would environmental and hereditary factors have more influence? Since I have not seen those data yet, I’ll continue to wear sunscreen and not eat bananas. Just in case.